This renewal proposal seeks continuing support for the NIH/CU Molecular Biophysics Training Program at the University of Colorado, Boulder. The goal of this 4-year old program is to prepare exceptional, highly motivated biophysics students for productive research careers. The 30 training faculty are an outstanding, internationally recognized group of investigators centered in three departments: Chemistry &Biochemistry;Molecular, Cellular &Developmental Biology;and Chemical &Biological Engineering. These faculties, together with their students, are using state-of-the-art biophysical methods to elucidate fundamental aspects of macromolecular structure, dynamics, mechanism, and function in systems ranging from single molecules to complex, multi-component assemblies. Molecular Biophysics is the most rapidly growing research field on the Boulder campus, where 12 new biophysical faculties have arrived in the past 5 years. An important driving force behind this growth is the NIH/CU Molecular Biophysics Training Program, which establishes a strong sense of community and inters- connectedness among biophysicists in different laboratories and departments. Moreover, the program maintains a rigorous training environment for predoctoral students of biophysics. The training program, which is supported both by NIH and by CU matching funds, ensures that predoctoral students receive the broad, interdisciplinary foundation needed to carry out cutting edge biophysical research. Training includes specialized coursework, laboratory rotations, and teaching duties during the first year. Training continues with additional coursework in the second year. Required courses include scientific ethics as well as biophysical courses developed by the program. Following the second year, students meet yearly with a faculty committee that provides independent mentoring for their thesis research. In all training years, regular Biophysics Seminars and Super group meetings maintain strong communication between biophysical students and faculty. During its first four years of NIH support the training program has flourished in multiple dimensions while benefiting from: 1) exciting new faculty, 2) growing student participation, 3) increasing quality of the selected trainees, 4) new courses, and 5) growing recruitment of minority and female students.